U.S. patent application number 09/911231 was filed with the patent office on 2002-02-07 for reciprocating pump standing head valve.
Invention is credited to Vann, Roy R..
Application Number | 20020014268 09/911231 |
Document ID | / |
Family ID | 26914806 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014268 |
Kind Code |
A1 |
Vann, Roy R. |
February 7, 2002 |
Reciprocating pump standing head valve
Abstract
A circular check valve with a central aperture is disclosed. The
preferred use as a standing head valve for reducing hydrostatic
pressure in a wellbore being produced by a reciprocating pump is
discussed. In this application the circular check valve allows the
a sucker rod, or equivalent source of pumping energy, to pass. The
device is attached to the pump barrel in communication with pump
chambers and the production tubing. The check valve device isolates
the pump internals and the formation from the hydrostatic head of
the produced fluid. The device eliminates pump-off and thus fluid
pounding resulting in more efficient pumping and less maintenance.
Other uses for the circular check are described.
Inventors: |
Vann, Roy R.; (Flint,
TX) |
Correspondence
Address: |
Charles W. Alworth
Alworth Law and Engineering
505 (Formerly 502) Cumberland Road
Tyler
TX
75703-9325
US
|
Family ID: |
26914806 |
Appl. No.: |
09/911231 |
Filed: |
July 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60220361 |
Jul 24, 2000 |
|
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Current U.S.
Class: |
137/515 |
Current CPC
Class: |
Y10T 137/7854 20150401;
Y10T 137/7845 20150401; E21B 43/127 20130101; E21B 34/06
20130101 |
Class at
Publication: |
137/515 |
International
Class: |
F16K 015/00 |
Claims
I claim:
1. A circular check valve comprising: a lower housing having a
first central axial aperture, an upper housing having a second
central axial aperture connected to said lower housing, and valve
means for controlling flow of fluid incorporating a third central
axial aperture sandwiched between said upper and lower housings
such that said central axial apertures are axially aligned with and
in communication with each other thereby axially forming a
continuous conduit through said lower housing, said valve means,
and said upper housing.
2. The device of claim 1 wherein an external member axially passes
through said continuous conduit.
3. The device of claim 2 further incorporating seal means located
in said upper housing for effecting a fluid seal between said upper
housing and said external member.
4. The device of claim 2 further incorporating seal means located
in said lower housing for effecting a fluid seal between said lower
housing and said external member.
5. The device of claim 2 further incorporating seal means located
in said valve means for effecting a fluid seal between said valve
means and said external member.
6. A circular check valve comprising: a lower housing having a
lower aperture, an upper housing connected to said lower housing
having an upper aperture, and valve means for controlling direction
of fluid flow incorporating a central axial aperture sandwiched
between said upper and lower housings such that said lower
aperture, said central axial aperture and said upper aperture are
axially aligned with and in communication with each other thus
forming a common aperture common to said upper housing, said lower
housing and said valve means.
7. The device of claim 6 wherein an external member axially passes
through said common aperture.
8. The device of claim 7 further incorporating seal means located
in said upper housing for effecting a fluid seal between said upper
housing and said external member whereby flow is diverted through
said valve means.
9. A circular check valve comprising: a lower housing having a
first axial center line and further having a flow opening centered
about said axial center line and in communication with said upper
flow housing, a plurality of flow apertures each in communication
with said flow opening, and whereby said flow opening axially
aligns with said axial center line; an upper housing having a
second axial center line connected to said lower housing and
further having an upper central aperture axially aligned with said
axial center line; valve means for controlling direction of fluid
flow having a third axial center line and further having a central
aperture axially aligned with said center line, and a plurality of
check valves axially arranged about said central aperture; wherein
said valve means is sandwiched between said lower housing and said
upper housing such that said plurality of check valves align with
said plurality of flow apertures within said lower housing and such
that when said lower and upper housing are attached to each other
said lower central aperture and said upper central aperture are
axially aligned with and in communication with each other forming a
common aperture.
10. The device of claim 9 wherein an external member axially passes
through said common aperture.
11. The device of claim 10 further incorporating seal means located
in said upper housing for effecting a fluid seal between said upper
housing and said external member whereby flow is diverted through
said plurality of flow apertures.
12. A circular check valve comprising: a lower housing having a
first axial center line and further having therein a lower housing
neck centered about said axial center line, an upper flow opening
centered about said axial center line, a lower flow opening
centered about said axial center line and in communication with
said upper flow housing, a plurality of flow apertures each in
communication with said upper flow opening, and a lower central
aperture extending through said neck, whereby said upper flow
opening, said lower flow opening and said lower central aperture
axially align with said axial center line; an upper housing having
a second axial center line connected to said lower housing and
further having therein an upper central aperture axially aligned
with said axial center line; valve means for controlling direction
of fluid flow having a third axial center line and further having
therein a central aperture axially aligned with said center line,
and a plurality of check valves axially arranged about said central
aperture; wherein said valve means is sandwiched between said lower
housing and said upper housing such that said plurality of check
valves align with said plurality of flow apertures within said
lower housing and said central aperture on said valve means
encircles said lower housing neck, and such that when said lower
and upper housing are attached to each other said lower central
aperture and said upper central aperture are axially aligned with
and in communication with each other forming a common aperture.
13. The device of claim 12 wherein an external member axially
passes through said common aperture.
14. The device of claim 13 further incorporating seal means located
in said upper housing for effecting a fluid seal between said upper
housing and said external member whereby flow is diverted through
said plurality of flow apertures.
15. The device of claim 12 wherein said upper housing has a top and
further comprising a fishing flange formed within said upper
housing near said top thereof.
16. The device of claim 12 wherein said upper housing has a bottom
side and wherein said plurality of check valves further consist of:
a ball housing having a fourth axial center line and further having
therein a plurality of balls, a plurality of ball apertures each
containing one of said plurality of balls, and a plurality of
finger apertures co-located with and in communication with said
ball apertures, said finger apertures capable of receiving fingers;
a finger housing having a fifth axial center line, a top, and a
bottom, and further having therein a plurality of fingers, equal in
number to said plurality of balls, wherein said plurality of
fingers are attached to said bottom of said finger housing pointing
axially away from said bottom and in line with said fifth axial
center line; and a spring located between said top of said finger
housing and said bottom of said upper housing; wherein said fingers
of said finger housing pass through said finger apertures of said
ball housing and come to rest on said balls.
17. A standing head valve for use in a wellbore comprising: a lower
housing having a first axial center line, a bottom, and further
having therein a lower housing neck centered about said axial
center line, an upper flow opening centered about said axial center
line, a lower flow opening centered about said axial center line
and in communication with said upper flow housing, a plurality of
flow apertures each in communication with said upper flow opening
and a lower central aperture extending through said neck, whereby
said upper flow opening, said lower flow opening and said lower
central aperture axially align with said axial center line; an
upper housing connected to said lower housing having a second axial
center line and further having therein an upper central aperture
axially aligned with said axial center line; a ball housing having
a third axial center line and further having therein a plurality of
balls, a plurality of ball apertures each containing one of said
plurality of balls, and a plurality of finger apertures, for
receiving fingers, co-located with and in communication with said
ball apertures; a finger housing having a fourth axial center line,
a top, and a bottom, and further having therein a plurality of
fingers, equal in number to said plurality of balls, wherein said
plurality of fingers are attached to said bottom of said finger
housing pointing axially away from said bottom and in line with
said fourth axial center line; a spring; wherein when said lower
and upper housing are connected said lower central aperture and
said upper central aperture are axially aligned with and in
communication with each other forming a common aperture, wherein
said ball housing, said finger housing, and said spring are
sandwiched between said lower housing and said upper housing such
that said plurality of balls align with said plurality of flow
apertures within said lower housing, said plurality of fingers pass
through said plurality of finger apertures and coming to rest on
said balls within said ball housing, and wherein said ball housing,
said finger housing, and said spring encircle said lower housing
neck.
18. The device of claim 17 wherein an external member axially
passes through said common aperture.
19. The device of claim 18 further incorporating seal means located
in said upper housing for effecting a fluid seal between said upper
housing and said external member whereby flow is diverted through
said plurality of flow apertures.
20. The device of claim 18 further incorporating seal means located
in said lower housing for effecting a fluid seal between said lower
housing and said external member whereby flow is diverted through
said plurality of flow apertures.
21. The device of claim 18 further incorporating seal means located
in said ball housing for effecting a fluid seal between said ball
housing and said external member whereby flow is diverted through
said plurality of flow apertures.
22. The device of claim 17 wherein said upper housing has a top and
further comprising a fishing flange formed within said upper
housing near said top thereof.
23. The device of claim 17 wherein a sand washer is placed at said
bottom of said lower housing.
24. The device of claim 17 wherein an adapter sub is attached to
said bottom of said lower housing.
25. The device of claim 20 wherein said adapter sub further has a
bottom and wherein a sand washer is placed at said bottom of said
adapter sub.
Description
[0001] This application claims priority from Provisional Patent
Application 60/220,361 filed on Jul. 24, 2000.
[0002] The present invention relates generally to the oil and gas
industry and in particular to stripper well production utilizing
reciprocating pumps.
BACKGROUND OF THE INVENTION
[0003] Marginal oil wells, better known as stripper wells, are
rarely operated by major oil companies because labor and pumping
costs are close to the sales revenue produced by the well, which
makes their operation uneconomic. Most oil and gas wells will
slowly reduce its hydrocarbon output and finally end up as stripper
wells. At this point, major companies will attempt to sell these
wells to small companies or plug and abandon the well.
Entrepreneurs who are able to scrounge up enough equipment and
control their labor and operating costs operate these small
companies; however, even their operating costs will slowly mount
and the well will be abandoned.
[0004] The actual definition of a stripper well is difficult to
come by, mainly because one person's (or company's) idea of a
stripper well will differ from another's. Generally a well is
considered to be a stripper well when it produces less than 10
barrels (420 U.S. gallons) of hydrocarbons per day. Stripper wells
are important to the economy of any country for they allow that
country to depend less on foreign supplies of hydrocarbons. This is
particularly important in times of international political
unrest.
[0005] With this in mind, it is desirable to develop and have
available novel oil well production equipment that is relatively
inexpensive and can be assembled from commercially available
materials. Novel equipment will allow an increase in the profit
gleaned from a stripper well. Novel equipment should have several
design points in mind. One, it should be easy to work on and
maintain. Two, it should be capable of operating at a low cost.
Three, it should operate the stripper well in such a manner that
the production rate will increase from marginal to profitable.
Thus, properly designed novel production equipment will increase
the number of profitable stripper wells and increase the overall
supply of valuable hydrocarbons.
[0006] Many stripper wells use a pump-jack unit that in turn
reciprocates a bottom hole pump. However, in a stripper, the flow
of fluid into the wellbore is limited (hence the term "stripper"),
and it is possible to run out of fluid. This condition is called
"pump-off." Pump-off occurs whenever the pump system attempts to
remove more fluid from the wellbore than is entering the wellbore
from the producing formation. Pump-off leads to destruction of the
downhole pump, the surface drive unit, and the intermediate
connection between the downhole pump and the surface unit. The
actual mechanism that causes destruction is termed "fluid
pounding."
[0007] Fluid pounding is encountered whenever pump-off occurs. The
lack of fluid in wellbore allows the introduction of compressible
gases into the wellbore. These gases generally come from the
formation or "outgas" from the wellbore fluid.
[0008] The downhole reciprocating pump consists of essentially two
parts, a moving chamber or pump plunger within a downhole assembly
or pump barrel. The pump barrel is attached to the production
tubing, which runs inside the wellbore to the surface. The pump
plunger lifts fluid from within the pump barrel into the production
tubing and onto the surface. On the upstroke, the plunger chamber
inlet valve is closed and fluid flows into the production tubing
making its way to the surface; whereas, on the downstroke, the
inlet valve is open. On the up stroke, wellbore fluids flow into
the pump barrel through a valve, at its base, that opens on the
upstroke and closes on the down stroke.
[0009] In normal circumstances, the pump plunger operates within a
liquid. The liquid in turn provides damping to the plunger, on the
downstroke, that absorbs the extension of the interconnection
assembly between the plunger and the surface power unit. The
interconnection assembly is generally a series of coupling rods -
named "sucker rods." The interconnection assembly could easily be a
wire cable. Materials expand (and contract) under load; thus, the
interconnection assembly will elongate under load. Under usual
circumstances, the downhole fluid absorbs the elongation.
[0010] Whenever pump-off occurs the pump accelerates into a gas
rather than a fluid on the downstroke of the pump. There is little
liquid to absorb or dampen the elongation, and the plunger strikes
or pounds the bottom portion of the pump barrel. Hence the term
--fluid pounding. The bottom of the plunger and the bottom of the
barrel both contain fluid inlet/check valves. Fluid pounding ruins
both valves. It also damages the interconnection assembly and the
surface power unit. Much consideration must be given to avoid
pump-off or fluid pounding.
[0011] There is one other cause of fluid pump-off. Many oil wells
which are in the their maturity begin to produce gas along with the
oil. This often results in fluid pounding even though the well is
not pumping-off. Quite often these wells are shut down, simply
because the cost of production, due to equipment problems, exceeds
or reaches the revenue derived from the well.
[0012] In the current art, the pump barrel inlet (check) valve
(sometimes called the standing valve), and the pump plunger inlet
valve and outlet check valve (sometimes called the traveling valve)
must operate against the wellbore hydrostatic head. Thus, when the
plunger lifts up, its inlet valve closes, and the barrel inlet
valve opens. The reduced pressure within the pump barrel caused by
the raising of the plunger allows the inlet valve to open. At this
point, formation fluid will enter the barrel. In a marginal well,
this fluid is a gas-liquid fluid, which is compressible. On the
down stroke, the barrel check valve will close. If the barrel fluid
is incompressible (i.e., no entrained gas), then the increase
pressure within the barrel, below the plunger, will force the
outlet valve of the plunger to open as the plunger approaches the
bottom of the pump barrel.
[0013] It must be remembered that as the plunger starts down, the
fluid pressure below the plunger within the barrel is at or near
formation pressure, which is lower than the hydrostatic head
pressure above the plunger outlet valve. Thus, the outlet valve
will not open until the pressure inside the pump barrel, below the
plunger, exceeds the hydrostatic pressure of the wellbore. As the
quantity of entrained gas builds up within the pump barrel below
the plunger, the pressure within the pump barrel below the plunger
will never exceed the hydrostatic head and the outlet and inlet
valves on the plunger will not open. This is pump-off. Because
there is little liquid to soften the downstroke, pounding
occurs.
[0014] Madden in U.S. Pat. RE. 33,163 (4,781,547) discloses a Gas
Equalizer for Downhole Pump. The Madden device operates in
conjunction with the traveling valve. Basically the Madden device
is designed to be fitted to an ordinary downhole pump and unseats
the traveling ball check valve, or outlet check valve, during most
of the downstroke of the plunger. In other words, the Madden device
forces the upper check valve to open without relying on the
increase in pressure within the plunger to force the valve open.
Madden states that, by forcing the upper check valve to open,
compressible fluid (gas) will be removed from the variable pump
chamber on each downstroke of the pump. This then allows the gas to
bubble through the production tubing to the surface. The Madden
device cannot relieve the downhole liquid column pressure (wellbore
hydrostatic head) on the downhole pump. Thus there is a limit to
the suitability of the Madden device.
[0015] Heath, U.S. Pat. No. 2,949,861 discloses a Pumping Rig and
Method. This device utilizes a downhole traveling valve; however,
Heath is only concerned with reducing the effective weight of the
sucker rods and does not address pounding or production problems
associated with wellbore hydrostatic head.
[0016] The economic factors influencing the abandonment of a
hydrocarbon well include operating costs, environmental issues,
costs of abandonment, etc. Operating costs are set by many factors:
labor price, distance from a maintenance base, available product
distribution networks, workover cost, and equipment repair costs.
The well must produce a profit. If any of the cost factors can be
reduced, that well may become profitable. If maintenance is
reduced, then the costs of labor and repair automatically come
down. Since fluid pounding is a major maintenance headache in
marginal wells, a technique to eliminate fluid pounding is needed.
Thus there remains a need for a device that will reduce the
effective wellbore hydrostatic head pressure and allow produced
fluid to enter a downhole pump chamber.
SUMMARY OF THE INVENTION
[0017] The instant invention simply adds a valve - called a
standing head valve - at the top of the pump barrel through which
passes the lift connection (polished rod) that is attached to the
pump plunger located within the barrel.
[0018] The standing head valve is designed to hold back the
wellbore hydrostatic head pressure, contained within the production
tubing, from the pump barrel (and the formation). Thus, at the
start of the downstroke, the plunger valve only sees the formation
pressure and readily opens to admit fluid. On the upstroke, the
standing head valve is forced open, and the plunger fluid
(formation fluid) passes through the standing valve into the
wellbore. On the downstroke, the standing valve closes, and
wellbore hydrostatic head pressure cannot be reflected into the
pump barrel. Essentially, the standing head valve adds another
check valve to the system.
[0019] The standing head valve is attached to the top of the pump
barrel and a special smooth rod, or polished rod, passes through
the center of the circular standing head valve. The polished rod
attaches to the sucker rods that form the intermediate connection
to the pump-jack on the surface. Of course other forms of
intermediate connections could be used, e.g., a Cable Actuated
Downhole Pump. (See for example the inventor's co-pending
application based on his Provisional Application 60/220,414, filed
on Jul. 24, 2000.)
[0020] The valve has essentially two functioning parts, which are
integrated. One of the parts is the special ring shaped, or
circular, check valve and the other part is the seal system through
which the polished rod passes. Because the standing head valve is
circular --set by the barrel of a standard pump --a special check
valve is required. The preferred circular check valve is plurality
of spring loaded metal balls operating within a plurality of
apertures set about the circular check valve. The seal system is
simple and comprises a smooth long rod (polished rod--available
off-the-shelf) with very close tolerances between the rod and the
inner diameter of the metal-to-metal seal.
[0021] Although the disclosure shows the use of the circular check
valve in a wellbore employed as a standing head check valve. The
concept could readily be employed in a service that requires
pressure control or flow control about a location through which a
reciprocating or rotating member must pass.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1 and 2 are a simplified illustration of a wellbore
showing the production tubing, a series of sucker rods terminating
in a polished rod that is connected to a pump plunger that in turn
operates within a pump barrel, and with the instant invention
connected to the top of the pump barrel.
[0023] FIG. 3 is a side view of the instant device.
[0024] FIG. 4 is a cut-away side view of FIG. 3.
[0025] FIG. 5 is a cross-section of FIG. 7 taken at A-A.
[0026] FIG. 6 is a cross-section of FIG. 7 taken at B-B.
[0027] FIG. 7 is an exploded view of the instant device showing all
parts.
[0028] FIG. 8 is a mechanical drawing illustrating a prototype of
the instant invention with the ball check valve in the closed
position.
[0029] FIG. 9 is a mechanical drawing illustrating a prototype of
the instant invention with the ball check valve in the open
position. In addition this figure illustrates several options to
the device.
[0030] FIG. 10 is a conceptual figure of the circular check valve
showing all optional seals and the check circular valve housing
sandwiched between the upper and lower housing.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0031] Referring to FIGS. 1 and 2, the instant invention, 10, is
shown in place on a standard art reciprocating pump system, 11, as
currently employed in the industry. As standard in the industry, a
hydrocarbon well has a casing, 9, through which the production
tubing, 8, extends. The downhole pump is usually attached to the
production tubing and powered by a series of connected sucker rods,
7.
[0032] The standing head valve, generally 10, prevents the wellbore
total hydrostatic pressure from resting on the top of the plunger,
3, and the plunger ball check or traveling valve, 4, on each
downstroke. If the full wellbore hydrostatic head is present, gas
can accumulate below the traveling valve, 4. Since gas is readily
compressed--unlike a liquid --the plunger will travel on its
downstroke to the bottom of the pump barrel without allowing the
produced gas and oil (total fluid) to travel through the plunger
into the upper plunger chamber, 2, located immediately above the
plunger ball check valve (traveling valve), 4.
[0033] When the above condition occurs, destructive forces are
induced and damage is inflicted on the pump unit. In addition, no
additional fluid will be available to be lifted to the surface.
I.e., no fluid enters the chamber in the downstroke for
transmission in the upstroke. The instant invention, 10, is
designed to hold all of the hydrostatic head pressure (that column
of fluid which from the bottom of the wellbore to the surface) away
from (or off of) the plunger, 3, and traveling valve, 4, during the
downstroke. This allows the fluid (produced gas and liquid) below
the plunger, 3, to pass by the traveling valve, 4, and into the
upper plunger chamber, 2, on each downstroke.
[0034] On the upstroke, all the fluid (liquid and gas) in the
plunger chamber, 2, is forced through the standing head valve, 10,
and to the surface. The produced gas that is forced into the liquid
column will act as "gas lift" in the fluid column. That is, the gas
acts to lighten the column and reduce the overall hydrostatic
head.
[0035] The instant invention, 10, when placed on the top of the
pump barrel, 1, causes the following series of actions to
occur:
[0036] A) On the upstroke, ball and seat valve 6 (the standing
valve) opens allowing produced liquid and gas to enter the barrel
below the plunger, 3, filling lower chamber, 5. Fluid that is in
upper chamber, 2, is pushed through the standing head valve, 10,
and onto the surface.
[0037] B) On the downstroke, ball and seat valve 6 (the standing
valve) is closed, ball and seat valve 4 (the traveling valve) is
opened, and plunger 3 travels towards the bottom allowing new
fluid, from the formation, to fill the upper chamber, 2, from the
lower chamber, 5. The pressure in the upper chamber, 2, will be the
same as the pressure in the lower chamber, 5, (i.e., formation
pressure) because the standing valve, 10, is holding back the
hydrostatic head of the fluid column.
[0038] C) The above steps are repeated. The strokes per minute are
set to match the rate of fluid production from the formation.
[0039] Remember that if gas and liquid are entering the pumping
system, ball and check valve, 4, (the traveling valve) will be
difficult to lift if there is no standing head valve, 10, in place
to keep the hydrostatic pressure off of the ball. In a 3000 foot
wellbore, the hydrostatic pressure will be approximately 1350 psi.
This figure will vary with fluid density and temperature. In this
example, the force required to open the traveling valve, 4, will
exceed 1350 psi. Very often formation gas moves through the ball
and seat valve (standing valve), 6, and it would take considerable
plunger movement to build a pressure above 1350 psi; therefore, the
traveling valve will remain closed and no fluid will enter the
upper chamber. With the standing valve in place, there is no such
backpressure and, therefore, fluid can flow more freely between the
lower and upper chambers.
[0040] Refer now to FIGS. 3 through 7. The instant invention
consists of a lower housing, 23, through which a plurality of flow
apertures, 30, along with a lower, 33, and upper flow openings, 34,
are bored.
[0041] The lower housing, 23 screws onto the top of the pump
barrel, 1 (see FIG. 1). As shown in FIG. 3, the threads of the
lower housing will match a standard intermediate pump barrel. If
the device is to be used with other standard pump barrels an
adapter sub, 21, with inside threads or and adapter sub, 22, with
outside threads is available. The proper adapter would be used
along with a further standard oil industry sub for attachment to
larger or smaller pump barrels.
[0042] An optional sand washer, 41, may be placed between the lower
housing and the pump barrel. This washer forms a "seal" between the
device and the production tubing, 8. The purpose of this seal is to
keep `flower sand` (an industry term for fine sand that is
sometimes produced with hydrocarbons) from building up and packing
around the device; thus, making it difficult to remove the
pump/device assembly for servicing. By using a cup washer at this
point, any flower sand build up will occur near the flow gap, 36,
which is an area of high velocity flow. The high velocity flow will
tend to stop build up of flower sand. The washer is made of a
suitable elastomer chosen to retain elastic properties at the
expected wellbore temperature (i.e., neoprene). A lower central
aperture, 38, passes through the lower housing and receives a
polished rod, 19. The lower central aperture, 38, the lower flow
opening, 33, and the upper flow opening, 34, are axial to each
other and in communication with each other as shown in FIG. 4.
Essentially, in manufacturing the lower housing, the central
aperture would be bored through the housing. The lower flow
opening, 33, is formed by boring out (enlarging) the lowest section
of the central aperture, 38, and the upper flow opening, 34, is a
further enlargement of the central aperture to allow a plurality of
flow apertures, 30, to be in communication the upper and lower flow
openings. The flow apertures terminate in at the surface of the
lower housing lip, 45, and a neck, 39, continues towards the top of
the lower housing.
[0043] The polished rod (an off-the-shelf item), 19, connects the
pump plunger, 9, (not a part of the invention) to the pump jack
sucker rods, 7, or alternate reciprocating pump lifting system.
Clearances between the central aperture and the polished rod are
tight--carefully set so that the metal to metal surfaces act as a
seal.
[0044] A plurality of flow apertures, 30, are formed within the
lower housing as shown in FIGS. 4 and 7 through 9. This plurality
of apertures is in communication with the inside of the plunger
barrel (upper pump chamber 2) and the inside of the production
tubing running to the surface. The flow apertures, 30, within the
upper end of the lower housing, terminate in a plurality of check
balls, 24. The upper end of flow apertures are slightly enlarged to
accept the balls and act as a ball seat. In other words, when the
balls rest against their respective aperture end, the aperture is
sealed. (That is, hydrostatic pressure is stopped from affecting
the system below the balls.)
[0045] To allow for upward movement of the balls (during the
upstroke), yet prevent the balls from falling away from the valve,
a ball housing, 25, is placed immediately above the lower housing
radially about the neck, 39, of the lower housing. The ball housing
has a plurality of apertures, 31, which accept the balls and align
with the flow apertures, 30, in the lower housing. Thus the balls
can move up and down within ball housing and within associated ball
aperture, 31. Immediately above the ball apertures, 31, are
associated finger apertures, 32. A locking pin or a locking screw,
40, is used to hold the ball housing in place on the valve body.
The ball housing contains a ball housing central aperture, 43,
which fits around the neck, 39, of the lower housing. To facilitate
manufacturing, and ensure that a flow gap, 36, will exist, a ball
housing lip, 46, is formed on the bottom side (nearest the lower
housing when assembled). The ball housing lip rests on the surface
of the lower housing lip, 45. The flow gap allows fluid that has
passed through the flow apertures to escape away from the
valve.
[0046] The locking pin or screw, 40, serves two purposes. The first
is to stop rotation of the ball housing radially about the lower
housing; thus, keeping the check balls over their associated flow
aperture. The second is to hold the ball housing in place during
assembly of the entire unit.
[0047] A finger housing, 27, is placed immediately above the ball
housing radially about the neck, 39, of the lower housing. A
plurality of ball fingers, 26, attached to a finger housing, 27,
pass downwards, through the finger apertures, 32, in the ball
housing, 25, and touch a respective ball, 24, in the ball housing,
25. The finger housing contains a finger housing central aperture,
44, which fits around the neck, 39, of the lower housing.
[0048] A spring, 28, is placed immediately above the ball finger
housing, 27, radially about the neck, 39, of the lower housing. The
spring and ball fingers act to hold the ball check valves against
an associated flow aperture in the lower housing, thus forming a
ball seal check valve. The spring is set to about 10 pounds, so
that on the upstroke--with ZERO hydrostatic head--the internal
pressure in the chamber must exceed roughly 20 pounds before the
ball seals open. These numbers are for illustration only and will
be set by the spring constant and the total area of the ball seals.
(Set by the size and number of balls.) An optional washer, not
shown, may be placed above the spring.
[0049] It should be noted that the check balls, 24, the ball
housing, 25, the ball fingers, 26, the finger housing, 27, and the
spring, 28, form an overall sub-assembly that is sandwiched between
the lower and upper housings. (See conceptual drawing, FIG. 10.)
Essentially this sub-assembly is a circular ball check valve. The
sub-assembly can be replaced with a series of flapper valves
co-located over the flow apertures, 30, to form an interesting
alternate check valve. The flappers can optionally be spring loaded
or allowed to operate under gravity. The flapper and the respective
action of the flapper can be considered to be similar to a swing
check valve--well known in the industry; but never used in this
manner. Machining of this alternate mode is difficult and in light
of the economics of the ball check valve is not the preferred
embodiment.
[0050] One of the key concepts in this disclosure is the use of a
circular check valve that allows for an external member (such as a
rod or tube) to pass internally through a check valve that in turns
holds back (checks) the reverse pressure or flow. Thus, any variant
of the preferred circular check valve would fall within the scope
of this disclosure. For example, other alternative check valves can
use well known variants of linear (in line) check valves such as
the common spring loaded plunger check valve. In the case of the
alternate embodiments, the linear independent check valves, 47,
(see FIG. 10) would be located in the "ball housing" and the finger
and finger housing would be redundant. Thus, in any embodiment of
the instant device, the circular check valve is essentially
sandwiched between the upper and lower housing.
[0051] In the preferred device, the lower housing, 23, screws into
the upper housing, 29, which retains the spring and finger housing.
Alternate embodiments may have the parts welded or bolted together.
The ball housing is retained by a pin or screw directly to the
lower housing as previously explained.
[0052] The upper housing, 29, like the lower housing, contains an
upper central aperture, 37, that passes axially through the upper
housing and receives the polished rod, 19. The aperture is
generally polished to form a metal-to-metal seal with the polished
rod. (It is possible to use another seal system to effect a seal
between the rod and the housing) This central aperture extends the
metal-to-metal seal between the polished rod and the standing head
valve. This seal is critical, for it prevents the hydrostatic
pressure from by-passing the ball seals.
[0053] The combined length of the lower central aperture in the
lower housing, 38, and upper central aperture in the upper housing,
37, is set by standard metal-to-metal seal criteria. Note that
these combined apertures form an overall common aperture, or a
continuous conduit, through the circular check valve. (One industry
standard sets one linear foot for 3000 feet of hydrostatic head as
a seal criterion.) Optionally, a neoprene seal is placed above the
sleeve to wipe the polished rod and prevent galling of the
metal-to-metal seal by dirt, sand, or other particles found in
wellbore fluids. The polished rod attaches to the sucker rods, 7,
which form the intermediate connection to the pump-jack, 11, on the
surface. Of course other forms of intermediate connections could be
used, e.g., a Cable Actuated Downhole Pump, as discussed in the
summary.
[0054] An optional seal system, 42, may be incorporated into the
upper housing in order to provide additional sealing. The optional
seal system shown uses two o-rings. Other seal systems, well known
in the industry, may be employed. For example, if a rotating
removable drive (passing through the center aperture) were used,
simple o-ring seal would not be appropriate and special seals would
have to be used. Such seals are seen to be a part of this
disclosure and may be placed in the upper or lower housing, the
circular check valve, both housings, or any combination thereof.
(Again see conceptual drawing, FIG. 10.)
[0055] The upper housing also includes a fishing neck, or flange,
35. Such a flange is a requirement of the industry and serves as an
attachment point for "fishing" the pump assembly from the wellbore
when and if required.
[0056] FIG. 8 shows the ball check valves in their closed position,
which is the expected position on a downstroke. FIG. 9 shows the
ball check valves in their open position, which is the expected
position on an upstroke. As explained, the ball valves are set to
open, against the spring, whenever the pressure (under zero
hydrostatic head) under the valve is greater than 20 pounds. Thus,
the standing head valve would open on an upstroke whenever the
upper pump chamber pressure exceeded 20 pounds plus the hydrostatic
head and would reseat when that pressure dropped below 20 pounds
plus the hydrostatic head. This valve may be adjusted by changing
the spring constant and a person skilled in the art of reciprocal
oil pump operation could easily determine the proper opening
pressure and associated spring constant.
[0057] As shown in FIGS. 8 and 9, the upper housing includes a
skirt, 48, to cover the spring, 28. The skirt is basically machined
as the body is manufactured. The skirt extends the upper housing
such that when the two housings are joined, the skirt covers the
spring and keeps borehole materials (sand, grit, fluids, etc.) from
contacting the spring, the finger housing, fingers, etc., and
interfering with the operation thereof. The cavity, formed by the
skirt between the upper and lower housing, in which the spring,
fingers, and finger housing travel, is filled with grease during
manufacture. Openings (with grease fittings or the equivalent) for
the addition of grease during maintenance and to allow `breathing`
can be added to the skirt. The skirt would not be needed in the
embodiments using alternate linear check valves.
[0058] As noted in the summary, the instant invention could be
employed in a location where isolation of pressure or directional
flow control is required while having an external member pass
through the isolating device. For example, the circular check valve
could be placed in water well service to control backflow from the
surface (or water system) into the aquifer. Numerous pumping
systems employ rotating pumps driven by a shaft from the surface
that lift water to the surface. Once past the surface head, water
then flows through a standard check valve and into the water
system. The instant device could be employed downhole, above the
aquifer, and protect the aquifer from pollution due to damaged
casing or the like. In this circumstance, the fishing neck may not
be required; however, it may be necessary to incorporate a seal
assembly, 42, in the upper housing to further seal the external
member that is passing through the common aperture. Other uses for
the instant device, a circular check valve with a center, central,
or common aperture (a continuous conduit from the top of the valve
through the bottom of the valve), will become apparent as the
device finds acceptance.
[0059] There has been disclosed the best and preferred mode for the
instant invention. Any dimensions and/or numbers, if given, are for
purposes of illustration only and should not serve to limit the
disclosure. For example, the figures show eight balls; however,
more or less would be utilized as required by valve size and
conditions of use. Industry standard pumps, polished rods, and the
like will set dimensions. An increase or decrease in the ball check
apertures, the use of flap valves or other forms of check valves,
and the like are within the concept of the disclosure. The key
disclosure is a circular check valve system with a central opening,
or common aperture, through which an external member (shaft,
polished rod, or likewise) may pass.
[0060] Although the disclosure illustrates a downhole wellbore
pump, the instant invention may find use with other equipment,
requiring a central aperture or opening through which an external
member may pass and in which control of hydrostatic head,
high-pressure discharge head, or flow direction, is needed.
* * * * *